"""Zero-shot time-series foundation-model (TSFM) methods (T1 only).

Three classes, all ``family="tsfm"``, ``tasks=frozenset({"T1"})``:

- :class:`Chronos2`  -- Amazon ``amazon/chronos-2`` decoder-only TSFM.
- :class:`Moirai2`   -- Salesforce ``Salesforce/moirai-2.0-R-small`` universal
                        TS transformer with distribution heads.
- :class:`TimesFM`   -- Google ``google/timesfm-1.0-200m-pytorch`` patch
                        decoder, ~200M params.

Contract (sklearn-style, per the unified-API plan)::

    M(*, task: str = "T1", config: <ConfigClass> | None = None)
    M.fit(X, y, *, seed: int = 42)              # ZS: no parameter learning;
                                                  # records the close-feature
                                                  # index from X shape
    M.predict(X) -> np.ndarray                  # (N, horizon) close trajectory
    M.save(path) / M.load(path)                 # HF save_pretrained + manifest

Hard rules (also enforced in ``tests/test_layer_isolation.py``):

* No benchmark IO. Loading HF model weights from the HF cache is fine; reading
  benchmark parquets is NOT.
* No eval imports.
* No ``meta`` consumption -- methods take only ``X`` (and at fit time, ``y``).
* No subsampling, canonical-index joins, or dataframe joins inside ``predict``.

Model-specific monkey-patches (preserved verbatim from the legacy
``baselines/tsfm.py`` runners; documented in
``methods/_vendored/CHANGES.md``):

* **Moirai 2.0 gluonts-0.16 wrap**: uni2ts 2.0 was validated against an older
  gluonts where ``Moirai2Forecast.forward`` returned ``outputs`` directly.
  gluonts >=0.16's ``QuantileForecastGenerator.__call__`` instead unpacks
  ``(outputs,), loc, scale = make_predictions(...)`` and iterates the batch
  calling ``output.T``, expecting ``(B, future_time, num_quantiles)`` so
  ``.T`` yields ``(num_quantiles, future_time)``. ``Moirai2Forecast`` forward
  returns ``(B, num_quantiles, future_time)`` -- we transpose into
  ``(B, future_time, num_quantiles)`` and wrap into the 3-tuple. Idempotent
  via the ``_macrolens_gluonts016_wrap_applied`` sentinel.

Sundial (THU) is NOT in the panel: its HF Hub modeling code requires
transformers 4.40.x, which conflicts with the rest of MacroLens
(transformers >=4.45 for vLLM 0.20 + Llama-4 / Gemma-4 / EXAONE FP8).
Time-MoE was dropped from the panel in 2026-05 due to NaN propagation
during long-horizon autoregressive prediction. Both are documented in
``methods/_vendored/CHANGES.md``.
"""

from __future__ import annotations

import json
import os
import pathlib
from typing import Any, ClassVar

import numpy as np
import pandas as pd

from ._config import (
    Chronos2Config,
    Moirai2Config,
    TimesFMConfig,
    TSFMConfig,
)
from ._registry import register
from .base import Method, _HFSaveMixin


_T1_ONLY = frozenset({"T1"})


# ── Shared helpers ────────────────────────────────────────────────────────


def _resolve_device(device: str) -> str:
    """Map the ``"auto"`` literal onto cuda-or-cpu, preserving explicit values."""
    if device == "auto":
        try:
            import torch

            return "cuda" if torch.cuda.is_available() else "cpu"
        except ImportError:
            return "cpu"
    return device


def _coerce_t1_input(X: Any) -> np.ndarray:
    """Validate / coerce a T1 X argument to a contiguous ``(N, L, F)`` float32 ndarray."""
    arr = np.asarray(X, dtype=np.float32)
    if arr.ndim != 3:
        raise ValueError(
            f"T1 TSFM predict expects X shape (N, lookback, F); got {arr.shape}"
        )
    return arr


def _close_panel(X: np.ndarray, target_idx: int) -> np.ndarray:
    """Slice the close column from a ``(N, L, F)`` panel."""
    if target_idx < 0 or target_idx >= X.shape[2]:
        raise ValueError(
            f"target_idx={target_idx} out of bounds for X with F={X.shape[2]}"
        )
    return X[:, :, int(target_idx)]


def _check_horizon(value: int | None) -> int:
    if value is None or int(value) <= 0:
        raise RuntimeError(
            "TSFM .predict requires a positive horizon, captured at .fit time "
            "from y.shape[-1]; got horizon = "
            f"{value}. Call fit(X_train, y_train) first."
        )
    return int(value)


def _maybe_set_deterministic() -> None:
    """Honour ``MACROLENS_DETERMINISTIC=1`` like the rest of the unified API."""
    if os.environ.get("MACROLENS_DETERMINISTIC", "0") != "1":
        return
    try:
        import torch

        torch.use_deterministic_algorithms(True)
        torch.backends.cudnn.deterministic = True  # type: ignore[attr-defined]
    except (ImportError, RuntimeError):
        pass


# ── Moirai 2.0 idempotent monkey-patch ────────────────────────────────────


def _apply_moirai2_gluonts016_wrap() -> None:
    """Bridge the uni2ts-2.0 / gluonts-0.16 forward protocol gap.

    Re-applies are no-ops thanks to the sentinel
    ``Moirai2Forecast._macrolens_gluonts016_wrap_applied``.
    """
    from uni2ts.model.moirai2 import Moirai2Forecast

    if getattr(Moirai2Forecast, "_macrolens_gluonts016_wrap_applied", False):
        return
    _orig_fwd = Moirai2Forecast.forward

    def _wrapped_fwd(self, *args, **kwargs):  # type: ignore[no-redef]
        preds = _orig_fwd(self, *args, **kwargs)
        return (preds.transpose(1, 2),), None, None

    Moirai2Forecast.forward = _wrapped_fwd
    Moirai2Forecast._macrolens_gluonts016_wrap_applied = True


# ── Common base for the ZS TSFM classes ──────────────────────────────────


class _TSFMBase(_HFSaveMixin, Method):
    """Mixin scaffolding shared by the three T1-only ZS TSFM classes.

    Subclasses must:

    * inherit and call this base ``__init__``,
    * implement ``_load()`` (to construct the model),
    * implement ``_predict_close(close, horizon)`` returning an ``(N, H)``
      float32 ndarray.
    """

    family: ClassVar[str] = "tsfm"
    tasks: ClassVar[frozenset[str]] = _T1_ONLY
    # ``_config_class`` is populated by the ``@register`` decorator on every
    # concrete subclass; declare it here so static type-checkers + the
    # ``default_config`` classmethod below resolve cleanly.
    _config_class: ClassVar[type[TSFMConfig]] = TSFMConfig

    @classmethod
    def default_config(cls) -> TSFMConfig:
        return cls._config_class()

    def __init__(
        self,
        *,
        task: str = "T1",
        config: TSFMConfig | None = None,
        **kwargs: Any,
    ):
        if task not in self.tasks:
            raise ValueError(
                f"{self.__class__.__name__}: unsupported task {task!r} "
                f"(supports {sorted(self.tasks)})"
            )
        self.task = task
        if config is None:
            config = self.default_config()
            if kwargs:
                config = type(config)(**{**config.model_dump(), **kwargs})
        elif kwargs:
            raise TypeError(
                f"{self.__class__.__name__}: pass either `config=` or kwargs, not both"
            )
        self.config = config
        self.target_idx: int = int(getattr(config, "target_idx", 0))
        self.device: str = _resolve_device(self.config.device)
        self._model: Any = None
        self._loaded: bool = False
        self._horizon: int | None = None

    # ── Subclass hooks ──

    def _load(self) -> None:
        raise NotImplementedError

    def _predict_close(self, close: np.ndarray, *, horizon: int) -> np.ndarray:
        raise NotImplementedError

    # ── Method API ──

    def fit(self, X: Any, y: Any, *, seed: int = 42) -> "Method":  # noqa: ARG002
        """Zero-shot fit: capture horizon from ``y`` and validate ``X`` shape.

        No parameters are learned. Subclasses override only if they need
        a context-window setup at this point (none of the four do).
        """
        _maybe_set_deterministic()
        Xa = _coerce_t1_input(X)
        ya = np.asarray(y, dtype=np.float32)
        if ya.ndim != 2 or ya.shape[0] != Xa.shape[0]:
            raise ValueError(
                f"T1 TSFM fit expects y shape (N, horizon) matching X (N, L, F); "
                f"got X={Xa.shape}, y={ya.shape}"
            )
        self._horizon = int(ya.shape[1])
        return self

    def predict(self, X: Any) -> np.ndarray:
        Xa = _coerce_t1_input(X)
        horizon = _check_horizon(self._horizon)
        if not self._loaded:
            self._load()
            self._loaded = True
        close = _close_panel(Xa, self.target_idx)
        out = self._predict_close(close, horizon=horizon)
        out = np.asarray(out, dtype=np.float32)
        if out.shape != (Xa.shape[0], horizon):
            raise RuntimeError(
                f"{self.__class__.__name__}._predict_close returned shape "
                f"{out.shape}; expected {(Xa.shape[0], horizon)}"
            )
        return out

    # ── HF save / load hooks (overridable) ──

    def _hf_save(self, path: pathlib.Path) -> None:
        """Default writer: HF ``save_pretrained`` if available, else torch.save.

        Always writes ``ft_state.json`` recording the captured horizon and
        ``target_idx`` so ``load`` can reconstruct without rerunning ``fit``.
        """
        path = pathlib.Path(path)
        ft_state = {
            "horizon": self._horizon,
            "target_idx": self.target_idx,
            "device": self.device,
        }
        (path / "ft_state.json").write_text(json.dumps(ft_state, indent=2))

        model = self._model
        if model is None:
            return
        save_pretrained = getattr(model, "save_pretrained", None)
        if callable(save_pretrained):
            save_pretrained(str(path))
        else:
            import torch

            torch.save(
                {"state": getattr(model, "state_dict", lambda: model)()},
                path / "state.pt",
            )

    def _hf_load(self, path: pathlib.Path) -> None:
        """Default loader: read ``ft_state.json`` then call ``self._load()``.

        Subclasses that want to read locally-saved weights instead of the HF
        hub override this; the four ZS classes don't fine-tune so the
        default (re-download from HF) is correct.
        """
        path = pathlib.Path(path)
        state_path = path / "ft_state.json"
        if state_path.exists():
            ft_state = json.loads(state_path.read_text())
            self._horizon = ft_state.get("horizon")
            self.target_idx = int(ft_state.get("target_idx", self.target_idx))
        # Re-load the underlying model (HF cache reuse keeps this cheap).
        self._load()
        self._loaded = True


# ── Chronos-2 ─────────────────────────────────────────────────────────────


@register(
    name="chronos2",
    family="tsfm",
    tasks={"T1"},
    config_class=Chronos2Config,
)
class Chronos2(_TSFMBase):
    """Amazon Chronos-2 zero-shot forecaster (``amazon/chronos-2``)."""

    config: Chronos2Config

    def __init__(
        self,
        *,
        task: str = "T1",
        config: Chronos2Config | None = None,
        **kwargs: Any,
    ):
        super().__init__(task=task, config=config, **kwargs)
        self._is_chronos2: bool = False

    def _load(self) -> None:
        # Auto-detect Chronos-1 (T5/Bolt) vs Chronos-2 via BaseChronosPipeline:
        # ChronosPipeline rejects Chronos-2's ``input_patch_size`` config field.
        import torch

        from chronos import BaseChronosPipeline, Chronos2Pipeline

        self._model = BaseChronosPipeline.from_pretrained(
            self.config.model_id,
            device_map=self.device,
            torch_dtype=torch.float32,
        )
        self._is_chronos2 = isinstance(self._model, Chronos2Pipeline)

    def _predict_close(self, close: np.ndarray, *, horizon: int) -> np.ndarray:
        import torch

        n, _ = close.shape
        batch_size = int(self.config.batch_size)
        all_preds: list[np.ndarray] = []
        contexts: list[Any] = []

        def _flush(ctx_batch: list[Any]) -> np.ndarray:
            if self._is_chronos2:
                # Chronos-2: predict_quantiles returns (quantiles, mean)
                # where ``mean`` is a list of (n_variates, horizon) tensors.
                # Univariate => take the (1, horizon) mean per item.
                _, means = self._model.predict_quantiles(
                    ctx_batch,
                    prediction_length=horizon,
                    quantile_levels=[0.5],
                )
                preds = np.stack([
                    m.squeeze(0).cpu().numpy() if hasattr(m, "cpu")
                    else np.asarray(m).squeeze(0)
                    for m in means
                ])
            else:
                # Chronos-1 (T5/Bolt): predict returns (B, num_samples, H).
                forecasts = self._model.predict(
                    ctx_batch,
                    prediction_length=horizon,
                    num_samples=int(self.config.num_samples),
                )
                preds = np.median(forecasts.numpy(), axis=1)
            return preds[:, :horizon].astype(np.float32)

        for i in range(n):
            contexts.append(torch.tensor(close[i], dtype=torch.float32))
            if len(contexts) >= batch_size:
                all_preds.append(_flush(contexts))
                contexts = []
        if contexts:
            all_preds.append(_flush(contexts))

        return np.concatenate(all_preds, axis=0)


# ── Moirai 2.0 ────────────────────────────────────────────────────────────


@register(
    name="moirai2",
    family="tsfm",
    tasks={"T1"},
    config_class=Moirai2Config,
)
class Moirai2(_TSFMBase):
    """Salesforce Moirai 2.0 zero-shot forecaster (``Salesforce/moirai-2.0-R-small``)."""

    config: Moirai2Config

    def __init__(
        self,
        *,
        task: str = "T1",
        config: Moirai2Config | None = None,
        **kwargs: Any,
    ):
        super().__init__(task=task, config=config, **kwargs)
        # Apply the gluonts-0.16 wrap eagerly + idempotently so multiple
        # Moirai2 ctor calls do not re-wrap (sentinel guard inside).
        try:
            _apply_moirai2_gluonts016_wrap()
        except ImportError:
            # uni2ts may not be installed at construction time; the wrap is
            # re-applied lazily inside ``_load`` if needed.
            pass

    def _load(self) -> None:
        from uni2ts.model.moirai2 import Moirai2Module

        _apply_moirai2_gluonts016_wrap()
        self._model = Moirai2Module.from_pretrained(self.config.model_id)

    def _build_forecast_model(self, lookback: int, horizon: int) -> Any:
        from uni2ts.model.moirai2 import Moirai2Forecast

        return Moirai2Forecast(
            module=self._model,
            prediction_length=horizon,
            context_length=lookback,
            target_dim=1,
            feat_dynamic_real_dim=0,
            past_feat_dynamic_real_dim=0,
        )

    def _predict_close(self, close: np.ndarray, *, horizon: int) -> np.ndarray:
        from gluonts.dataset.pandas import PandasDataset

        n, lookback = close.shape
        forecast_model = self._build_forecast_model(lookback, horizon)
        predictor = forecast_model.create_predictor(batch_size=1)

        preds = np.empty((n, horizon), dtype=np.float32)
        for i in range(n):
            ts_df = pd.DataFrame(
                {"target": close[i].astype(np.float32)},
                index=pd.date_range("2024-01-01", periods=lookback, freq="B"),
            )
            ds = PandasDataset({"target": ts_df})
            forecasts = list(predictor.predict(ds))
            if not forecasts:
                raise RuntimeError(
                    f"Moirai predictor.predict returned no forecasts on "
                    f"instance {i}; refusing to silently substitute persistence."
                )
            median_pred = forecasts[0].median[:horizon]
            preds[i] = np.asarray(median_pred, dtype=np.float32)
        return preds


# ── TimesFM ───────────────────────────────────────────────────────────────


@register(
    name="timesfm",
    family="tsfm",
    tasks={"T1"},
    config_class=TimesFMConfig,
)
class TimesFM(_TSFMBase):
    """Google TimesFM 1.0 zero-shot forecaster.

    Default checkpoint: ``google/timesfm-1.0-200m-pytorch``.
    """

    config: TimesFMConfig

    def __init__(
        self,
        *,
        task: str = "T1",
        config: TimesFMConfig | None = None,
        granularity: str = "daily",
        **kwargs: Any,
    ):
        super().__init__(task=task, config=config, **kwargs)
        self._granularity = granularity
        self._loaded_horizon: int | None = None

    def _load(self) -> None:
        # No-op here: TimesFm requires `horizon_len` at construction time, so
        # the actual instantiation is deferred to ``_ensure_loaded(horizon)``.
        return

    def _ensure_loaded(self, horizon: int) -> None:
        import timesfm

        if self._model is not None and self._loaded_horizon == horizon:
            return
        self._model = timesfm.TimesFm(
            hparams=timesfm.TimesFmHparams(
                backend="gpu" if str(self.device).startswith("cuda") else "cpu",
                per_core_batch_size=int(self.config.per_core_batch_size),
                horizon_len=horizon,
            ),
            checkpoint=timesfm.TimesFmCheckpoint(
                huggingface_repo_id=self.config.model_id,
            ),
        )
        self._loaded_horizon = horizon

    def _predict_close(self, close: np.ndarray, *, horizon: int) -> np.ndarray:
        self._ensure_loaded(horizon)
        freq_map = {"daily": 0, "weekly": 1, "monthly": 2}
        freq_code = freq_map.get(self._granularity, 0)

        n, _ = close.shape
        out: list[np.ndarray] = []
        batch_size = int(self.config.batch_size)
        for start in range(0, n, batch_size):
            ctx = close[start : start + batch_size]
            forecasts, _ = self._model.forecast(
                [c.tolist() for c in ctx],
                freq=[freq_code] * len(ctx),
            )
            arr = np.asarray(forecasts, dtype=np.float32)[:, :horizon]
            out.append(arr)
        return np.concatenate(out, axis=0)


__all__ = [
    "Chronos2",
    "Moirai2",
    "TimesFM",
    "_apply_moirai2_gluonts016_wrap",
]